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Relationship between Stabilizer (CYA) and FC?

I have read a lot of stuff on the Forum and I have learned a lot so far. Still have a lot to learn .

There is something that shows up very often in discussion in different threads that I don't get at all. It's the proper chlorine level (FC) based on my CYA level. For instead, it is illustrated in "Chemgeek's Best Guess Chart" here http://troublefreepool.com/sticky.php

My questions on the topic are:

1) Why do I have to keep more FC depending on my CYA level?

2) Very often, Forum members say it is a bit different for salt pool using a SWG. I have a SWG and I would like to know why it is different with a SWG?

3) If I try to keep my CYA level between 60 - 80 ppm, what should be my FC with a SWG?

Because CYA (stabilizer) binds to a certain amount of the chlorine and keeps it from being effective.

I'll take a SWAG at the SWG question. I'm not an expert on SWG but I think the difference is you can handle a higher CYA when you have SWG because of the higher concentration of chlorine at the manufacturing point. It could be a bit caustic, if it were actually fully effective at that point. You also don't have to worry as much because it is producing fresh chlorine regularly (as long as you run your pump, enough).

Hopefully, one of the SWG pro's will be along soon to either blow my theory or give you better info on that.

Buggs

14,000 gallon, in ground, plaster, free form, play pool.
Sta-Rite Max-E-Glass with a 1.5 hp Emerson motor
WaterCo Micron High Rate sand filter S750 490 lb, 4883 sq ft - using ZeoBest
In floor Polaris cleaning system
Blue Diamond robot for those after storm days when I can't wait overnight for the in floor to clean it.

Re: Relationship between Stabilizer (CYA) and FC?

Originally Posted by BIC

I have read a lot of stuff on the Forum and I have learned a lot so far. Still have a lot to learn .

There is something that shows up very often in discussion in different threads that I don't get at all. It's the proper chlorine level (FC) based on my CYA level. For instead, it is illustrated in "Chemgeek's Best Guess Chart" here http://troublefreepool.com/sticky.php

My questions on the topic are:

1) Why do I have to keep more FC depending on my CYA level?Because the chlorine combines with the CYA to form chlorinated isocyanurates. While these test as FC they actually are not and do not have the sanitizing power of hypochlorous acid, which is what FC is. Only some of the hypochlorous acid combines with the CYA but the more CYA the more that combines so a higher CYA level needs more hypochlorous acid in the pool to leave the same amount left uncombined. IF the CYA is high but the FC is not raised to compensate for this then there is a higher amount of clorinated isocyanurates and less hypochlorous acid in the water.

2) Very often, Forum members say it is a bit different for salt pool using a SWG. I have a SWG and I would like to know why it is different with a SWG?Because of the way the chlorine is constantly introduced into the pool and beause the very high chlorine level in the cell is constantly 'supershocking' the water as it passes through the cell. It has been found from emperical results that salt pools can operate very well at a lower FC even though the CYA is much higher. When they need to be shocked they still need to be raised to about 20 ppm however. The good news is that salt pools rarely, if ever, require shocking.

3) If I try to keep my CYA level between 60 - 80 ppm, what should be my FC with a SWG?3-5 ppm has been found to work very well. It is also very important to make sure the pH does not rise above 7.8 since this can cut down on chlorine production drastically!BIC

Re: Relationship between Stabilizer (CYA) and FC?

Originally Posted by waterbear

Originally Posted by BIC

I have read a lot of stuff on the Forum and I have learned a lot so far. Still have a lot to learn .

There is something that shows up very often in discussion in different threads that I don't get at all. It's the proper chlorine level (FC) based on my CYA level. For instead, it is illustrated in "Chemgeek's Best Guess Chart" here http://troublefreepool.com/sticky.php

My questions on the topic are:

1) Why do I have to keep more FC depending on my CYA level?Because the chlorine combines with the CYA to form chlorinated isocyanurates. While these test as FC they actually are not and do not have the sanitizing power of hypochlorous acid, which is what FC is. Only some of the hypochlorous acid combines with the CYA but the more CYA the more that combines so a higher CYA level needs more hypochlorous acid in the pool to leave the same amount left uncombined. IF the CYA is high but the FC is not raised to compensate for this then there is a higher amount of clorinated isocyanurates and less hypochlorous acid in the water.

2) Very often, Forum members say it is a bit different for salt pool using a SWG. I have a SWG and I would like to know why it is different with a SWG?Because of the way the chlorine is constantly introduced into the pool and beause the very high chlorine level in the cell is constantly 'supershocking' the water as it passes through the cell. It has been found from emperical results that salt pools can operate very well at a lower FC even though the CYA is much higher. When they need to be shocked they still need to be raised to about 20 ppm however. The good news is that salt pools rarely, if ever, require shocking.

3) If I try to keep my CYA level between 60 - 80 ppm, what should be my FC with a SWG?3-5 ppm has been found to work very well. It is also very important to make sure the pH does not rise above 7.8 since this can cut down on chlorine production drastically!BIC

Thanks a lot waterbear & Buggsw. That does answer my qyuestions very well.

I have not received my TF pool kit yet. It should arrived around Monday. I bought an temporarly Kit until I get the TF Kit. I have noticed that my actual Kit do not test FC higher than 3 ppm. That becomes very difficult to judge where I'm at with FC (3, 4 or 5 ppm ). I'm assuming that the TF pool kit will measure FC up to at least 5 ppm. In case I have to shock the pool (a day), does the kit go up to 20 ppm. If not, how do you measure FC up to 20 ppm?